SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'e523970933d8b5065abdd9996694a5848633c433a254b3a9024cc7f653f2fad0' 
  AND token = 'UbcmX+So2OLaNzuuP4jRXRFU7sI9P2LZwxHhSixjeLI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

{
  "query_block": {
    "select_id": 1,
    "message": "no matching row in const table"
  }
}